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Yamaha CA-2010 Relay issue

TommyW

TommyW

Active Member
I just picked up a Yamaha CA-2010 for cheap I found on FB marketplace. The protect relay on the PS board works sporadically. I noticed that when it does NOT engage, I am reading ~300mv idle current even though it's set to Normal Operation mode. Switching the operation mode back and forth does not change the idle current. When the protect relay does engage, the idle current reads ~25mv and switches back and forth from 25mv to 300mv when I change the operation from Normal to Class A. I've removed and cleaned the Operation Relay contacts as I thought it might have been sticking. I also checked the Power Supply board for any cold solder joints. Should I just replace the protection relay? Any advice would be appreciated. Also, the DC offset has been adjusted on both channels to less than 5mv per the service manual.
 
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TommyW said:
~25mv and switches back and forth from 25mv to 300mv when I change the operation from Normal to Class A
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It is suppose to switch from 25mv to 280mv. 300 is a little high but not cause any issues other than create a little more heat.
 
When toggling the Class A / NORMAL switch does the relay physically set and reset? Do a visual.
 
Might just be a bad solder connection on the PS board. Reflow solder connections on TR401 and 402 on the Power Supply board. Need to verify a stable DC voltage at +B3 pin/lug. Should be in the 12 vdc ballpark.
 
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avionic said:
Might just be a bad solder connection on the PS board. Reflow solder connections on TR401 and 402 on the Power Supply board. Need to verify a stable DC voltage at +B3 pin/lug. Should be in the 12 vdc ballpark.
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It is closer to 280mv, although the service manual says to set it to 300mv. I am going to check those solder joints on TR401 and TR402. I am only getting 1.5v on +B3.
 
avionic said:
Might just be a bad solder connection on the PS board. Reflow solder connections on TR401 and 402 on the Power Supply board. Need to verify a stable DC voltage at +B3 pin/lug. Should be in the 12 vdc ballpark.
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Re-flowed the solder joints on those two transistors. Pulled and tested them also. They tested good. No difference.
 
TommyW said:
I am only getting 1.5v on +B3.
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There is your problem. +B3 is the power supply for all three relays. Check fuse F402 continuity with a multimeter. F402 is on the power supply board.
 
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avionic said:
There is your problem. +B3 is the power supply for all three relays. Check fuse F402 continuity with a multimeter. F402 is on the power supply board.
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All of the fuses are good. I did not realize there were 3 relays. I think I may have found the issue. D404(1s1885) was reading reverse of what I would expect for a diode on my DMM. I replaced it with a IN4007(didn't have an IN4004) and it is engaging now.
 
avionic said:
Hmm. I don't think I have ever found a bad flyback diode (D404). So, is class A and protect relay now working as they should?
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Yes they are both working. Switching to Class A engages the relay and changes the idle voltage to 280mv(I adjusted down a little from service manual). The diode(D404) was showing forward voltage drop with my positive lead on the cathode/negative on anode and with my negative lead on the cathode/positive on anode it was reading 'OL'. I'm still not 100% it's fixed as it has been working sporadically, but +B3 voltage looks good now. I appreciate your help. You got me pointed in the right direction.
 
avionic said:
Fingers crossed.. :biggrin: :rockon:
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Hah. I spoke too soon and jinxed myself. It worked like 3 or 4 times in a row, and now I'm back to 1.5v on +B3 and the relay is not engaging. I tested TR402 and TR401 while I had them out earlier and they both tested good, but I am thinking of replacing them. Voltages are off on both, except I am getting 16v to the collector of TR402.
 
avionic said:
Fingers crossed.. :biggrin: :rockon:
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So I assume the two brown wires are coming from +B3 are the 12V feeds for the other relays. From my observation, the 12v is only supplied when the relay on the PS board engages. What other transistors are involved in the protection circuit? I could not find the protection circuit description in the service manual.
 
Look at D402 and R403 100Ω 1/4 watt carbon film. C403 10µf/ 25v (Z) could be shorted as well.
 
avionic said:
Look at D402 and R403 100Ω 1/4 watt carbon film. C403 10µf/ 25v (Z) could be shorted as well.
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So it was working last night before I went to bed. This morning it was not working. I pulled C403 and C406(both purple caps). C403 had a 22uf/25v capacitor installed instead what the service manual specifies(10uf/25v). Both were way out of spec, so I replaced and now it working again, but for how long I don't know.
 
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